In the present study, we investigated the tumor arsing from the T-cell area of the lymph node. Peripheral T-cell lymphoma (PTCL) was classified according to the updated Kiel (Suchi) classification. The clinicopathologic, phenotypic and genotypic findings of node-based, low-grade, PTCL (AILD type, T-zone type, and lymphoepithelioid type) were summarized (Cancer 1991 ; 67 : 2565). The proportion of the neoplastic cells (CD4+, Ki67+) in these tumors was demonstrated to have a relatively good correlation with the clonal TCRbeta rearrangement (Cancer 1993 ; 72 : 1762, Acta Pathol Jpn 1993 ; 43 : 396). In the process of the (Cancer 1993 ; 71 : 249). An accumulation of the additional 10 cases of this tumor suggested them to constitue a unique subgroup regarded as high-grade lymphoma, although some might be of natural killer (NK) cell lineage.Interdigitating cell sarcoma was an extremely rare tumor arising from the paracortical area in the lymph node (Cancer 1988 ; 61 : 562). Recently, we described the histologic and immunophenotypic features of four cases of this tumor (Pathol Int 1994 ; in press).We are going to examine the participation of oncogene and antioncogene in those tumors.